In such orbital sanders/grinders which are known in practice, the center of gravity of the balancing weight lies on the theoretical connecting line between the two rotational axes of the eccenter er eccentric, i.e. in terms of the rotational axis in the housing diametrical to the rotational axis of the eccenter in the disk holder. Thus when the orbital sander/grinder is raised from the workpiece, practically all forces generated in the disk holder and revolving about the rotational axis of the eccenter in the housing are compensated for in this manner.
At least when the thus balanced sander/grinder is pressed against the surface of the workpiece, cutting forces occur which in terms of the rotational axis of the eccenter generate a torque in the housing and thus generate transverse forces that act upon the eccenter and revolve about the rotational axis of the eccenter in the housing in accordance with the orbital motion of the disk holder. These transverse forces which constantly change direction are translated by the disk holder to the housing or the handle. The transverse forces occurring at the handle are felt by the operator as annoying oscillations.
In addition it may occur--at least in larger orbital sanders/grinders--that the elastic couplings by which the disk holder is fastened to the housing already generate considerable transverse forces when the disk holder is brought into oscillating or orbital motion in relation to the housing. In such cases a balancing weight, whose center of gravity lies in the theoretical continuation of the normal line bisecting the two rotational axes, would result only in inadequate balancing.